1. Field of the Invention
The present invention relates to a projector apparatus configured to process a light emitted from a light source by an optical device and project the processed light as a projection light image onto a screen through a projection lens.
2. Description of the Related Art
Conventionally, this type of projectors, for example, a liquid crystal projector comprises a light source, an optical device including a deflection plate, a liquid crystal panel and a prism, a projection lens and the like, which are mounted within a main body. The liquid crystal panel generally includes, as light bulbs, three liquid crystal panels corresponding to light's three primary colors for processing (modulating) each color light according to image information. The light emitted from the light source is separated into each color light, which is then processed (modulated) according to image information by each liquid crystal panel through the deflection plate, and composed into a projection light image through the prism or the like. The composed projection light image is enlarged and projected onto the screen by the projection lens.
Such a projector is associated with a risk of not being able to obtain a desired projection light image due to an adverse effect such as deformation on the optical device by the main body internally heated with the heat generated from the light source or the optical device. As a countermeasure against such an adverse effect, the heat of the optical device and the light source has been released by setting a plurality of fans within the main body and supplying (blowing) air (external air) outside the projector by each fan. In this case, the heat release with external air can be sufficiently performed in the light source since the light source reaches an extremely high temperature of about +900° C., while the optical device has a relatively low upper limit of operating temperature and, for example, the upper limit of operating temperature capable of ensuring stable operation without deformation or the like is as low as several tens degrees C. in use of a liquid crystal panel as the optical device. Therefore, the amount of heat release in this optical device is greatly influenced by the external air temperature. Namely, although the optical device can sufficiently release the heat to the supplied external air when the external air temperature is low, the amount of heat release must be ensured by increasing the air volume of the fans when the external air temperature is high. This results in problems such as remarkably increased power consumption in addition to increased noise by the operation of the fans.
Further, the problem of a so-called short cycle of air after heat release is also caused, in which although the external air which receives the heat is discharged to the outside, this discharged external air is sucked again by the fan and supplied to the projector, and a sufficient heat release effect cannot be obtained.
To solve such problems, for example, the following techniques for cooling the optical device including the liquid crystal panel have been proposed: a system for cooling the optical device with air cooled by a low-temperature part by providing a cooling device including the low-temperature part formed by a refrigeration cycle for circulating refrigerant (refer to Japanese Patent Application Laid-Open No. 2008-112094; Patent Document 1) and a system for cooling the optical device with low-temperature air created by electronic cooling (refer to Japanese Patent Application Laid-Open No. 2005-121250; Patent Document 2).
According to the system of Patent Document 1, dew condensation is caused on an evaporator that is the low-temperature part of the refrigeration cycle by the operation of the cooling device. Since the area for disposing the evaporator as the low-temperature part of the refrigeration cycle is not partitioned from the area for disposing the optical device in this system, dew adhered to the evaporator and/or dew fallen from the evaporator evaporate in accordance with a rise of ambient temperature upon stoppage of the operation of the cooling device, and resulting moisture adheres to the optical device, whereby the optical function is deteriorated. A detailed explanation of this phenomenon follows. Although the temperatures of the evaporator and the optical device naturally rise upon stoppage of the operation of the cooling device, the optical device including the prism is slow in temperature rise, and if the dew adhered to the evaporator and/or the dew fallen from the evaporator evaporate due to the rise of temperature of the evaporator in a state where the optical device is cooled, resulting moisture adheres to the optical device including the prism, causing the deterioration of the optical function. Particularly, the adhesion of the moisture to the prism causes deterioration of the composing function as projection light image, resulting in a situation such that a desired image cannot be obtained when the composed projection light image is enlarged and projected onto a screen by a projection lens.
Although the problem of the noise can be solved by the electronic cooling as disclosed in Patent Document 2, this electronic cooling is poor in energy efficiency, and requires a means for releasing heat to external air (heat sink or fan) in the vicinity of a cooling object since a heating part of the electronic cooling is integrally constituted, and a spatial restriction caused thereby leads to a remarkable deterioration of design flexibility. Further, when the electronic cooling operation is stopped, dew adhered to a cooling part of the electronic cooling evaporates, causing the same problem as in Patent Document 1.
According to the cooling system of Patent Document 1, a high cooling effect can be obtained since optical elements of a color composition optical system are locally forcedly cooled using the cooling device. However, the conventional projector apparatus further has the problem of a dew condensation countermeasure to be solved in addition to such a temperature countermeasure. Although this problem is never caused if a second section having the optical elements of the color composition optical system disposed therein is perfectly sealed and internally perfectly dehumidified in Patent Document 1, even a slight clearance allows penetration of humid external air during the operation, causing dew condensation on the surface of the optical elements of the color composition optical system after stopping the operation.
In the conventional projector apparatus containing the cooling system, a cooler (evaporator) of the cooling system faces a cold air circulating path for cooling the color composition optical system, and the cooler has a temperature equal to that of the color composition optical system during the operation of the apparatus. However, the temperature of the cooler immediately starts rising upon stoppage of the operation due to its high heat exchange efficiency, while the rise of temperature is delayed in the optical elements of the color composition optical system since a color composition prism and a condenser lens particularly have large heat capacities. In such a state, dew condensation water adhered to the cooler or dew condensation water collected in a dew condensation water storage part starts evaporating, and steam thereof adheres to the surface of the optical elements which are in a low-temperature state, compared with the cooler, or in a temperature state of dew condensation point or lower, causing the dew condensation thereon.
Such dew condensation on the surface of the color composition prism or the condenser lens obviously affects generation of projection light, and cleaning of the surface is also indispensable since stain or dust left on the surface after evaporation of the dew condensation deteriorates the quality of projection image. However, since the part in which each optical element is disposed is a structurally little part, the cleaning operation is not easy, and even if the cleaning operation is performed, the optical elements or wirings may be damaged. Therefore, this part is desired to be maintenance-free.